High site fidelity, strong associations, and long‐term bonds: Short‐finned pilot whales off the island of Hawai‘i

Abstract

Studies of short-finned pilot whales suggest they travel in stable mixed-sex groups composed of strongly associated individuals; however, temporal analyses of social structure are lacking. To examine site fidelity, association patterns, and temporal relationships, we analyzed data from 267 encounters of this species off the island of Hawai'i from 2003 through 2007, identifying 448 distinctive individuals (68.1% seen more than once). About 72% of the whales were linked by association into a single social network, suggesting the possibility of multiple populations using the area. Sighting histories suggested that only some individuals exhibit high site fidelity. Individuals demonstrated preferential associations and community division was strongly supported by average-linkage hierarchical cluster analysis of the association data. Nine longitudinally stable social units composed of key individuals and their constant companions were identified. Qualitative assignment of age and sex classes of unit members indicated that some segregation between adult males and female/ calf pairs may occur. Temporal analyses of individuals encountered on the same day indicate stable long-term associations. Differential patterns of residency and site fidelity were unexpected and may be indicative of multiple populations around the main Hawaiian Islands. The presence of a resident population demonstrating strong, long-term site fidelity and associations off Hawai'i Island may warrant special management considerations.

Movement and foraging behavior of short-finned pilot whales in the Mid-Atlantic Bight: importance of bathymetric features and implications for management

“…Comparisons of the movements, foraging behavior, and habitat associations of short-finned pilot whales in the SAB and MAB are needed in order to assess whether there might be separate stocks of short-finned pilot whales in the US Atlantic EEZ, and to determine whether foraging behavior might play a role in maintaining stock structure. In addition to broad-scale geographical differences in foraging behavior, pilot whales have long-term social bonds which could lead to foraging specializations within social groups (Amos et al 1993, Ottensmeyer & Whitehead 2003, Mahaffy et al 2015. Tracks from multiple individuals within different social groups are required to investigate how social structure might influence foraging behavior bet ween groups of shortfinned pilot whales in the MAB.…”

False killer whale and short-finned pilot whale acoustic identification

“…Both species occur in largely overlapping distributions in tropical to warm temperate waters of all oceans, generally in more offshore and deep waters , 2013a,b, Bradford et al 2014, Mahaffy et al 2015. Behavioral and genetic evidence indicates 3 distinct populations of false killer whales in Hawaiian waters, with an insular main Hawaiian Islands stock, a pelagic, offshore stock, and a Northwestern Hawaiian Islands stock (Chivers et al 2010, Baird et al 2012, 2013a, Bradford et al 2014, Martien et al 2014.…”

Acoustic differentiation of Shiho- and Naisa-type short-finned pilot whales in the Pacific Ocean

“…1). In Hawai'i, these recordings come from at least 15 known social clusters (as defined in Mahaffy et al, 2015), within at least two hypothesized island communities in the insular population of short-finned pilot whales. Social structure data are not available from the eastern Pacific Ocean; however, it is likely, due to both the spatial and temporal distance between encounters and the large population size in the region, that each encounter represents a different social group in that region.…”

“…Then, because short-finned pilot whales are known to form stable social groups (Mahaffy et al, 2015), we used a nested, non-parametric multivariate analysis of variance (MANOVA) to test whether encounters (roughly equal to social groups) might cause statistical differences between regions, implemented in R using the BiodiversityR package (Kindt and Coe, 2005).…”

“…Evidence suggests that, for other social cetaceans, variability in the vocal repertoire can be both socially driven [e.g., killer whales (Yurk et al, 2002;Riesch et al, 2006;Deecke et al, 2010;Filatova et al, 2012;Crance et al, 2014;Musser et al, 2014) and sperm whales (e.g., Rendell et al, 2012;Cantor et al, 2015)] and behaviorally driven [e.g., killer whales (Filatova et al, 2013;Holt et al, 2013)]. Shortfinned pilot whales are a highly social cetacean, known to form stable social groups for a decade or more (HeimlichBoran and Hall, 1993;Mahaffy et al, 2015). In the Hawaiian Islands, these social groups form island-associated communities within a Main Hawaiian Island insular population (Baird, 2016).…”